Group vi-b transition metal-amino-phosphorodithioates and method for producing same

ABSTRACT

GROUP VI-B TRANSITION METAL-AMINO-PHOSPHORODITHIOATES, WHICH ARE THE REACTION PRODUCTS OF AMINE SALTS OF GROUP VI-B OXYACIDS AND PHOSPHORODITHIOIC ACIDS, ARE DISCLOSED. A PROCESS FOR PRODUCING THE BEFORE-MENTIONED COMPOUNDS IS ALSO DISCLOSED THAT COMPRISES CONTACTING AN ACIDIC AQUEOUS MEDIUM CONTAINING THE GROUP VI-B METAL SOURCE WITH A WATER-IMMISCIBLE ORGANIC MEDIUM CONTAINING AN ALKYL AMINE AND RECACTING SAID PRODUCT WITH A PHOSPHORODITHIOIC ACID AND RECOVERING THE COMPOUNDS OF THIS INVENTION. LUBRICATING COMPOSITIONS CONTAINING THE COMPOUNDS OF THIS INVENTION ARE ALSO DISCLOSED.

United States Patent 3,598,848 GROUP VIB TRANSITION METAL-AMINO-PHOS-PHORODITHIOATES AND METHOD FOR PRO- DUCING SAME Phyllis Dodds, Wysox,and Vincent Chiola, Towanda, Pa., assignors to Sylvania ElectricProducts Inc. No Drawing. Filed Sept. 5, 1968, Ser. No. 757,788 Int. Cl.C07f 11/00; Cm 1/48 U.S. Cl. 260429R 14 Claims ABSTRACT OF THEDISCLOSURE BACKGROUND OF THE INVENTION Ths invention relates tooil-soluble Group VIB transition metal-amino-phosphorodithioates, toprocesses for producing same and to lubricating oil compositionscontaining the compounds.

Present day lubricating oils and greases contain various additives thatimpart to the compositions desirable characteristics such as detergency,antioxidant, antisludge, anticorrosion and antiwear properties. Toachieve a suitable composition several additives generally have to bea'dded.'

For example, zinc dialkyldithiophosphates, which are produced byneutralizing the reaction product of phosphorus pentasulfiide and analcohol with sodium hydroxide and thereafter replacing the sodium ionswith zinc ions in an aqueous medium impart some of the abovecharacteristics such as antioxidant, antiwear and anticorrosionactivity. Other materials such as the amine salts of molybdic ortungstic acid are used to impart sludge djspersancy, high temperaturedetergency and antifriction properties. Other additives which are usedinclude the adducts of the Zinc phosphorothioates and alkylene oxidessuch as the lower alkylene oxides having an alkylene radical containing6 or less carbon atoms. The materials are used to impart improveddetergency and corrosion resistance to the oil composition. In eachinstance, however, more than one additive is required to achieve many ofthe desired characteristics. It is believed, therefore, than an additivecontaining more of the desired properties in a single compound therebyreducing the number of additives required is an advancement in the art.Furthermore, it is believed that the process for producing suchcompounds, due to its flexibility and simplicity, is also an advancementin the art.

SUMMARY OF THE INVENTION In accordance with one aspect of thisinvention, there is provided new compositions which are the reactionproducts of the amine salts of the various Group VI-B oxyacids and thecompounds of the formula 2 I RiO1lSH S Formula 1 wherein R and R areeach hydrocarbon radicals selected from the group consisting of alkyl,aryl and alkaryl, having from about 1 to about 30 carbon atoms.

A second aspect of this invention is the process for preparing saidcompounds. The process is relatively free of operating difficulties andhas a large degree of flexibility, and in general, involves:

(1) Contacting an aqueous medium comprising water and a water-solubleGroup VIB transition metal source, said medium being at a pH of below 7,preferably at a pH of from about 0 to about 4, with a water-immiscibleorganic medium comprising a water-immiscible solvent and an alkyl amine,for a time suflicient to extract at least some of the transition metalfrom the aqueous medium into the organic medium thereby forming anamino-Group VI- B transition metal reaction product;

(2) Separating the organic and aqueous mediums;

(3) Recovering the Group VIB transition metal-aminophosphorodithioiccomposition by providing the following steps, in any order:

(a) adding a phosphorodithioic acid to the amino-Group VIB transitionmetal reaction product, and

(b) removing the organic, water-immiscible solvent from the organicmedium thereby recovering the compounds of this invention.

If desired, the process of this invention can be carried out in adifferent sequence of operating steps with equally good results.Therefore, in accordance with another embodiment of this invention, anaqueous medium comprising water and Group VIB transition metal source Iis contacted with a water-immiscible organic medium com- For a betterunderstanding of the present invention, to{ gether with other andfurther objects, advantages and capabilities thereof, reference is madeto the following disclosure'and appended claims in connection with theabove description of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The Weight percentage of theGroup VIB transition metal can be varied depending upon the quantity ofGroup VIB transition metal desired in the additive and will be dependentupon the amount of the foregoing metal present in the aqueous solutionand the amount of the dialkyl phosphorodithioic acid used in theprocess. For example, the molybdenum containing compositions of thepresent invention will generally contain from about 610% by weight ofsulfur, 2-4% by weight of phosphorus, 27% by weight of molybdenum andfrom 12% nitrogen. The Weight percentages of the foregoing componentswill vary depending upon the molecular weight of the Group VIBtransition metal that is used. For example, the foregoing compositionswherein tungsten is the Group VIB transition metal, will contain fromabout 4 to about 7% sulfur, about 1-3% phosphorus, about 213% tungstenand from about 0.5 to 1.5% nitrogen. With chromium-containingcompositions the Weight percentage of chromium is decreased with thecorresponding increase in the other elements due to its lower molecularweight. The Group VIB transition metal containing radical will in mostinstances be the transition metallic oxycations represented by theformula M O wherein M is the Group VIB transition metal, x is an integerfrom 1-30, y is an integer from 1-90 and the valence of M O is from 1 to15. The compounds of this invention, therefore, enable a large degree offlexibility which was heretofore only achieved by blending severaladditives.

Lubricating oils which can be used as the base oils to which the newcompounds of this invention are added are not limited as far as theeffectiveness of the compounds are concerned, therefore, lubricationoils that are of a lubricating viscosity can be used. For example, oilsthat have a naphthenic base, paraflinic base and other hydrocarbonbases, as well as lubricating oils derived from coal products andsynthetic oils, such as the alkylene polymers, alkylene oxide polymers,dicarboxylic acid esters, alkylated benzene, silicate esters, siliconpolymers and the like are suitable.

In general, any water-soluble Group VI-B transition metal source can beused, that is a material which contains chromium, molybdenum or tungstenand that is soluble to the extent of at least 0.1 gram per 100 grams ofwater at 25 C. Suitable sources of Group VI-B transition metals includewater-soluble Group VIB transition metal oxides, Group VI-B transitionmetal oxyhalo compounds, Group VLB transition metal peroxy compounds,ammonium and alkali metal salts of Group VI-B transition metalperoxyacids. The alkali metal salts of the Group VI-B transition metalperoxyacids, such as sodium, potassium and lithium molybdates, sodiumpotassium and lithium tungstates and the like, are preferred with thesodium salts being especially preferred. Although any of the Group VIBtransition metals, that is either chromium, molybdenum or tungsten canbe used, molybdenum and tungsten are preferred.

In most instances, an aqueous solution having a Group VI-B transitionmetal concentration of from about 1% to about by weight is preferred. Insome instances concentrations of as low as about 0.1% by weight can beused, however, these lower concentrations are not preferred since thereare no additional beneficial results achieved from using the lowerconcentrations and the excess water can create disposal problems.Although higher concentrations can be used such as those containing ametal concentration greater than about by weight, such highconcentrations generally approach saturated solutions which can resultin either a yield loss or require recycle of the aqueous medium. The pHof the aqueous medium is below about 7 with a pH of from about 0 toabout 4 being preferred in most instances. Use of a higher pH preventsextraction and formation of the compounds of this invention.

The phosphorodithioic acids which can be used in practice of thisinvention are well known in the lubricating art and in general containtwo hydrocarbon radicals selected from the group consisting of alkyl,aryl and alkaryl and from about 1 to about carbon atoms. As is known inthe art, since the phosphorodithioic acids are often prepared frommixtures of alcohols and phosphorus pentasulfide, the carbon atomcontent of the hydrocarbon group is an average value for the mixture.For example, one of the preferred phosphorodithioic acids is one inwhich the hydrocarbon radicals are alkyl groups having an average chainlength of about 5 carbon atoms. In some instances, however, relativelypure phosphorodithioic acids are produced and these are also good rawmaterials. For example, one of the preferred raw materials is di-isotylphosphorodithioic acid.

When the amines are described herein as being waterinsoluble, it ismeant that less than about 0.1 gram will dissolve in 100 cc. of water at25 C. When the amines are described herein as soluble in thewater-immiscible organic solvent, it is meant that greater than about0.1 gram, will dissolve in 100 cc. of the organic solvent at 25 C. Theamines which are suitable therefore, are the alkyl amines that aresoluble in a water-immiscible, organic solvent of a class to behereinafter described and insoluble in water. These useful amines arealkyl amines selected from those of the formula /Ra NIB! R5 wherein R Rand R are each selected from the group consisting of hydrogen and alkylcontaining from about 3 to about 30 carbon atoms and wherein at leastone of R R and R is alkyl and the total number of carbon atoms is fromabout 3 to about 60 carbon atoms. The alkyl groups can be eitherstraight or branched cham and can be a mixture of compounds containingalkyl radicals of varying chain lengths but having a given averagevalue. The amines as described above can be either primary, secondary ortertiary amines. For example, suitable primary amines includetrialkyl-methyl amines of the formula Formula 2 R Formula 3 wherein R,,,R and R are each alkyl radicals containing from i to about 20 carbonatoms. Typical commercially available amines of the above class arethose wherein two of the radicals represented by R,.,, R and R inFormula 3 above are methyl and the other radical can vary from about 15to about 21 carbon atoms.

Suitable secondary alkyl amines that are water insoluble and organicsolvent soluble are selected from amines of the formula R'NH Formula 4wherein R and R" are each alkyl containing from 3 to .30 carbon atoms.For example, a commercially available suitable amine is an amine whereinR is an alkyl radical containing from about 11 to about14 carbon atomsand R" is an undecyl radical.

Tertiary amines, that is those of the formula Re lid-1 1 R Formula 5wherein R R and R are each alkyl radicals containing from about 3 toabout 30 carbon atoms. The R groups can be either straight or branchedchain and can be the same or different radicals. Commercially availableamines include those of Formula 5 wherein R R and R,- each vary fromabout 8 to about 13 carbon atoms.

It has been found that the volumetric ratio of the amine to the solventin the organic medium should be between about l0z90 to about :10. Use ofhigher and lower concentrations reduces the efliciency of the process,therefore, are not generally used.

The organic solvents which can be used in the practice of this are thosethat are essentially immiscible with water, that is those that have asolubility of less than 0.1 gram of solvent/ cc. of water at 25 C. andhave a boiling point less than about 250 C. In most instances thearomatic organic solvents, that are immiscible with water, such asbenzene, toluene, cumene, xylene, naphthalene and other petroleumfractions containing aromatic hydrocarbons that have boiling pointsbelow about 250 C., will be used. If desired, however, the solvent canbe selected from the cycloparaffins that have the foregoingWater-immiscible and boiling point properties, such as cyclohexane,cyclopentane and the like. Although the solvent can have a boiling pointas high as 250 C., since the solvent is subsequently removed from thecompounds of the present invention, normally by distillation, it ispreferred to use solvents having relatively low boiling points, that isbelow about C. with those having a boiling point of below about 120 C.being especially preferred. Since the process is carried out in liquidphase, on order to avoid potential losses of solvent or the use ofpressurized equipment, it is generally preferred to use solvents havinga boiling point above about 50 C.

The time the aqueous and organic media are in contact is immaterial froman operative standpoint, however, in order to achieve relatively highyield, without recycle, the contact time should be sufiicient to extractessentially all of the Group VIB transition metal into the organicphase. In most instances, when the aqueous solution concentra tion oftransition metal is within the preferred range as heetofore specified,the length of contact is not excessive, that is generally below about 10hours. Since the organic and aqueous media are readily separable, it isgenerally relatively simple to determine if the extraction is complete.For example, after the organic and aqueous media have been in contactfor a reasonable period of time, that is, longer than about 30 minutes,the two media can be allowed to separate by allowing them to standwithout agitation and then sample one of the media and analyze for thepresence of the transition metal. In most instances the aqueous mediumwill be analyzed to determine the degree of extraction that hasoccurred. As previously mentioned, the organic and aqueous mediaseparate easily, therefore conventional techniques for the separation ofimmiscible liquids can be used such as gravity separating, decanting andthe like.

After the two media are separated, the phosphorodithioic acid can beadded either to the organic medium and thereafter the solvent removed orthe solvent can be removed before the addition of the phosphorodithioicacids. In most instances it is preferred to add the acid prior toremoval of the solvent because the amino-transition metal salts arerelatively viscous. In most instances distillation will be the preferredmethod of removing the organic solvent for either media. As can beappreciated the solvent can be condensed and recycled if desired.

To further illustrate certain embodiments of the present invention, thefollowing non-limiting examples are presented. All parts, proportionsand percentages are by weight unless otherwise indicated.

Example I Four solutions containing 50, 60, 70, and 85 percent by volumeof a mixture of trialkyl straight chain symmetrical tertiary amines inbenzene are contacted with equal volumes of 3 M H 80 The amines mixtureis about 60% tridecyl amine and about 40% trioctyl amine. An aqueoussolution of sodium tungstate is acidified to pH 2 with sulfuric acid.The concentration of tungsten in the aqueous solution is about 200grams/liter, W basis. Equal volumes of organic and aqueous phases arecontacted for about 20 minutes. After settling, aliquots of both phasesare taken and isotope studies showed 599% extraction of tungsten fromthe aqueous medium to the organic medium. The organic medium is retainedand the benzene is evaporated to isolate the active ingredient which isa viscous salt. The viscous salts are mixed with equal volumes ofdi-isoctyl phosphorodithioic acid and heated to obtain the reactionbetween the salts and acid bath. The liquid product is soluble in 10Wmotor oil.

Example II Organic solutions A, B, and C containing 70% by volume ofthree dilferent amines in benzene are contacted with equal volumes of 3M H 80 The three amines used are given in the following solutions:

(A) A mixture of amines having the formula R-GNH,

wherein the R groups are alkyl containing from about 15 to about 21carbon atoms.

(B) A mixture of amines having the formula wherein the R group containsfrom about 11 to about 14 carbon atoms and R contains about 11 carbonatoms.

(C) A mixture of amines having the formula wherein the R groups are C Hhaving different degrees of branching.

The amine solutions are then contacted for about 30 minutes with equalvolumes of an aqueous solution of Na WO acidified to pH 2, with sulfuricacid and containing about 200 g./liter, W0 basis. After settling, theaqueous phases are analyzed for tungsten. About 210 g./l., W0 basis, isextracted into the organic media based upon the analysis of the aqueousphases. The amount of sulfur, as contained in the dithiophopshoricacids, needed to react with the tungsten in the organic media to form W5is calculated, and about 36 volumetric parts of a C-8 dialkylphosphorodithioic acid are added to 100 volumetric parts of theamine-tungsten salts and gently heated. A 1% solution, by volume, isadded to 10W motor oil. All are soluble and compatible with allcommercial motor oils.

Example III Essentially the same procedure is used as in Example Iexcept that various phosphorodithioic acids are used in conjunction withvarious amines. Samples of the reaction product are analyzed for S, P,and W. Results of analysis are given below.

Phosphorodi Wt. percent thioic acid S P W E 4. 82 2. 6 12. 38 F 4. 57 2.24 12.27 E 5. 31 2. 66 12. 00 F 5. 12 1. 78 11. 39 E 6. 37 2. 45 3. F 5.05 1. 47 3. 58 E 7. 09 2. 67 2. 49 F 6. 40 1. 60 4. 24

1 D=Amine as described in Example I.

Z E=A mixed dialkyl phosphorodithioic acid wherein the alkyl groupscontain various chain lengths with an average value of 5 carbon atoms ineach alkyl group.

3 F=Di-isooctyl phosphorodithioic acid.

Infrared absorption spectra are obtained on each of the above samples.All samples have strong lines at 680, 980, 1165, 1380 and 2940 cm.-Samples 1 and 2 have two additional strong peaks at 1520 and 1620 emfand Samples 3 and 4 have one additional strong peak at about 1600. Theabove results indicate some differences in patterns when differentamines are used. For example, Samples 1 and 2 were produced from aprimary amine. Samples 3 and 4 were produced from secondary amines,while Samples 58 were produced from tertiary amines. Moderate absorptionpeaks were attained on all samples at 670, 880, 1205, 1370, 1440, 1500,3040 and 3400 cm.

Example IV Essentially the same procedure as in Example III is followedexcept that molecular equivalent amounts of sodium molybdate aresubstituted for the sodium tungstate. Samples of the reaction productsare analyzed for weight percent S, P and Mo. Results of these analysisare given below. I

.Phosphok Wt. percent Infrared absorption spectra are obtained on allsamples.

Strong absorption peaks appear at 680, 980, i165, 1470 and 2940 cm.-Moderate peaks appear at 600', 615, 710,

2880, 3040 and 3100 CIIl. The same strong lines appear when primary andsecondary amines are used as were present in Example III.

Example V Samples of lubricating oil compositions are prepared by.dissolving about by volume of the compositions prepared in Examples IIIand IV in 10W motor oil. Samples of the above lubricating compositionswhen heated .to about .120 C. for about 2 hours. indicated no sludgeformation. When heated in the presence of aluminum and lead indicate nocorrosion of either metal. The above tests indicate the properties whichare suitable as additives for lubricating compositions.

The compositions of this invention Will be used in amounts of less thanabout 10% by weight of the total lubricatingcomposition. In mostinstances at least about 1% of the composition will be used. It is alsoto be noted that often it can be advantageous to produce a relatively 4concentrated solution containing a lubricating oil and a major amount ofthe compositions of this invention then add this solution to. thelubricant to yield a mixture havingthe foregoing percentages by weightof the composition of this invention.

While there has been shown and described what is at present consideredthe preferred embodiments of the inv vention, it Willbe obvious to thoseskilled in the art that various changes and modifications may be madewithout departing from the scope of the invention as defined by theappended claims? We claim:

1. A process for producing an oil-soluble, Group VI-B transitionmetal-amino-phosphorodithioic compositions, suitable for usea'salubricating oil additive, said process comprising:

contacting an aqueous medium, having a pH of below about 7, andcomprising water and a Group VI-B H transition. metal source, with awater-immiscible organic medium comprising a water-immiscibleorganicsolvent andan alkyl amine, for a time sufficient V to extract at leastamajor portion of said transition metal from said=aqueous medium intosaid organic medium thereby forming an amino-Group VI-B transition metalreaction product; separating said organic medium and said aqueousmedium; and recovering the Group VI-B transitionmetal-aminophosphorodithioic composition by providing the followingsteps in any order:

product.

2. A process according to claim 1 wherein said Group VI-B transitionmetal is tungsten.

,3. A process according to claim 1 wherein said Group VIB-'-transitionmetal is molybdenum.

4. A process according to claim 1 wherein said amine is selected fromthe group consisting of primary, secondary and tertiary alkyl aminescontaining from about 3 to about 60 carbon atoms.

5. A process according to claim 4 wherein said organic solvent is anaromatic hydrocarbon solvent.

6. A process according to claim 5 wherein said Group VIB transitionmetal is tungsten.

7. A process according to claim 5 wherein said Group VI-B transitionmetal is molybdenum.

8. A process--for producing an oil-soluble Group VI-B transitionmetal-amino-phosphorodithioic compositions, suitable for use asalubricating oil additive, said process comprising:

contacting anaqueous medium having a pH of below about 7 and comprisingwater and a Group VI-B transition metal source, with a water-immiscibleorganic medium comprising a water-immiscible organic solvent, an alkylamine and a phosphorodithioic acid, for a time sulficient to extract atleast a major portion of said transition metal from said aqueous mediuminto said organic medium, thereby forming an amino-Group VI-B transitionmetal phosphorodithioic reaction product;

separating said organic medium and said aqueous medium; and

recovering the Group VI-B transition metal-aminophosphorodithioic'composition by removing said water-immiscible organic solvent.

19. A process according to claim 8 wherein said Group VLB transitionmetal i's tungsten.

10. A process according to claim 8 wherein said Group VI-B transitionmetal is molybdenum.

'11. A process according to claim 8 wherein said amine is selected fromthe group consisting of primary, secondary and tertiary alkyl aminescontaining from about 3 to about carbon atoms.

12. A process according to claim 11 wherein said organic solvent is anarbmatic hydrocarbon solvent.

13. A process according to claim 12v wherein said Group VI-B transitionmetal is tungsten.

14. A process according to claim 12 wherein said Group VI-B transitionmetal is molybdenum.

References Cited UNITED STATES PATENTS 2,737,492 3/1956 Beegle et a125232.7 3,114,712 12/1963 'Spengler et a1. 25246.4 3,282,838 11/1966"Knowles et al. 25249.7 3,290,245 12/196'6 Elliott et a1. 25232.73,351,647 11/1-967 Butler et a1. 260-4293 TOBIAS E. \LEVOW, l 'rimaryExaminer A. P. DEMERS, Assistant Examiner US. Cl. X.R.

1252l32.7E; 260438.5R, 429K

